Joining ACS 2015 Data with Census Block Shape files 2015

Hi There,

I'm trying to join the demographics from ACS 2015 data with Block Shape files from 2015 on BlockGroupID (Block Group FIPS code) and see some of Block groups are missing from ACS that are in Census Shape file. I'm wondering what is the reason behind this. I'm new to this kind of geographic data and the group itself. Would love to hear some expect options on how I can get complete information.

Hi Mohammed - have you checked to see if there is any population data for the missing block groups? That would be what I'd look for first - if there is no population in the block group then there would be no reason for there to be a record for that in the ACS data.

I'm not sure which data tables you are using from ACS 2015, but there is some data suppression for geographies where the margins of error are larger than the estimates. You can see an explanation and list of affected tables here: www.census.gov/.../2016-01.html

Hi Jami - Thanks for getting back. I realized that I framed my question incorrectly.
Yes, you are right these block groups are not present in ACS 2015 but they are present in Census Shapefile 2015. And my question would be why are they present in Census but not in ACS ? And Census 2010 has some population associated with these block groups, my thinking is
1) Is that because ACS does not capture all block groups but census does
2) or, there are changes over time in the geographical block groups, they are merged or broken out every year depending on lot of factors?

So the tables mentioned in the link might not have all the block groups in them ? Good to know. Anyways I combined all the 22 demographic tables/files into one and replaced columns codes with names for our convenience to do analytics.

You are correct that the tables mentioned in the link might have missing block groups, but that doesn't explain your problem.

I think something might be going wrong with your data processing, or else there is a problem with the national block group files. I looked at the South Dakota state geodatabase from the link you provided and I don't see the geographies that you list as missing in the geometry file or the data tables. And looking at the missing Virginia block group numbers, I don't think they exist either (there is no county with code 515).

David Stinchcomb Yes I guess that answers my question, now is there a historical database/file that tracks all of these changes every year ? I saw the link you sent but that has it in different HTML pages, hard to track/read in any software.

Thanks to both of you by the way. I'm new to this so learning some new things.